This invention relates generally to mechanical timers, and in particular to mechanical timers used to control various water softening cycles such as backwash, brine draw, brine fill and rinse.
Water softening systems of the ion exchange type often include a tank having a bed of ion exchange resin, such as a polystyrene resin. The resin material is usually non-soluble and effectively acts as a permanent anion to which exchangeable cations, such as sodium ions (Na+) can attach. During the softening process, the hardness-causing ions in the water, such as calcium (Ca++) and magnesium (Mg++) ions are exchanged with the xe2x80x9csoftxe2x80x9d sodium ions of the resin bed, thus producing softened water. This exchange occurs because the calcium and magnesium ions have a stronger affinity toward the resin bed than do the sodium ions. After prolonged contact of the resin bed with hard water, however, the ion exchange capacity of the resin bed diminishes, and regeneration of the resin bed must be performed.
Regeneration of the resin bed is normally performed in distinct steps during what is called the regeneration cycle. First, the bed is cleansed during a backwash cycle, where the normal water flow across the resin bed is reversed to expand the resin bed and remove any deposits that may be trapped in the resin bed. Second, a brine solution (i.e., an aqueous solution of sodium chloride or the like) from a separate brine tank is introduced to the resin bed. When the brine contacts the resin bed, the aforementioned ion exchange process is reversed, i.e., the xe2x80x9chardxe2x80x9d ions in the resin bed are replaced with xe2x80x9csoftxe2x80x9d ions from the brine solution. Thereafter, a rinse cycle is normally provided to wash the brine from the resin bed. Lastly, the brine tank is refilled to form brine for the next regeneration cycle.
It is known to utilize mechanical timers to control the various regeneration cycles. Additionally, due to the particular demands placed upon the water softening system, it is often desirable for a user to vary the length of time for each individual regeneration cycle to adjust for various tank sizes and volumes of resin To accomplish this, mechanical regeneration timers may use movable fingers to time the individual regeneration cycles, such as the timer disclosed in U.S. Pat. No. 5,590,687. However, such timers often require disassembly or use of tools by the user to adjust the individual cycle times. This usually entails the removal or loosening of covers, screws, or other fasteners to access and/or move the regeneration cycle time adjustments. Disassembly of this nature is normally awkward and time consuming for users of water softening systems. Thus, there is a need for a mechanical timer to control water softener cycle times that allows users to easily and efficiently adjust the individual cycle times without any disassembly of the timer mechanism or use of tools.
These and other needs will become apparent upon a further reading of the following detailed description taken in conjunction with the drawings.
In one form of the invention, the aforementioned needs are fulfilled by a mechanical timer to control multiple steps of a process comprising a first cam having a shaft, and a second cam having a shaft, wherein the shaft on the first cam extends into the shaft of the second cam. The rotational relationship between the first and second cams determines the length of time for at least one process step. First and second user adjustable elements are attached to the first and second cams. These user adjustable elements do not require any disassembly of the mechanical timer by the user or require any tools. A plurality of switches engage the cams to control various process steps.